The present invention relates to a medical device, namely, an apparatus for generating air pulses to be delivered to the chest of a patient for treatment and diagnostic purposes.
It has been recognized that applying pneumatic pressure to the chest wall of a patient has both diagnostic and treatment applications. Typically, a bladder or other type of air-receiving chamber is positioned about the chest of a patient. An air flow generating system is coupled with the bladder. The air flow generating system selectively controls the air pressure in the bladder to provide the desired compressions of the patient's chest.
One application of applying pneumatic pressure to a patient's chest is breathing assistance. A patient may not require a ventilator, yet need some assistance for adequate breathing. For example, a patient may be able to inhale, but not fully exhale. A bladder and air flow generating system is coupled with a system for detecting the breathing cycle, i.e., exhalation and inhalation. When the patient's exhale cycle is detected, a controlled air pulse is delivered to the bladder, "squeezing" the patient's chest to provide a greater exhalation. The air flow generating system then reduces the bladder pressure, allowing the patient to freely inhale on the next breathing cycle.
Pneumatic chest compression is also used for airway mucous mobilization. For example, high frequency chest compressions are used as a treatment to clear the airways of cystic fibrosis patients, see, e.g., U.S. Pat. Nos. 5,453,081, 5,056,505, and 4,838,263, incorporated herein by reference. Airway mucous mobilization may also be useful in the therapy regime of other respiratory ailments, including emphysema, asthma, and chronic bronchitis. Additionally, mucous mobilization may also be useful in diagnostic applications. For example, there is some indication that early stages of lung cancer may be detected by analyzing cell material in a patient's mucous. Enhanced mucous mobilization using chest compressions may generate better mucous samples and, consequently, better cancer detection opportunities.
Pneumatic chest compression is also useful in diagnostic procedures that measure the concentration of one or more exhaled gases. In one application, the measurement of nitric oxide indicates the extent of inflamed tissue in the airway of patients with various disease states. Such measurements are very precise and minute, with concentration levels in parts per billion. The concentrations of the gases are flow and pressure dependent; consequently, a specific and constant exhalation rate and pressure is desirable while performing such measurements. Therefore, there is a need for a chest compression system that operates to maintain constant exhaled air flows and pressures. This system should include a fast response control loop linked to a real time flow and pressure monitor in a patient's mouth.
Additionally, pneumatic chest compression may be useful in a diagnostic system for determining the condition of airways in patients with respiratory problems. For example, airways can be restricted by the effects of mucous build-up, muscle spasms, or inflammation. The pattern of air flow in a patient's mouth can be measured in response to a cycle of precise pressure variations on the chest wall. By accurately maintaining chest pressure variations, any variations in air flow at the patient's mouth are the result of changes in the restriction of the airways. To further identify the cause of the airway restriction, a broncho-dilator is used to determine if muscle spasm is causing the airway restriction. Additionally, a mucous mobilization mode is used to determine if mucous is causing the restriction.
Further, pneumatic chest compression may improve the efficiency, speed, and/or depth of deposition of aerosol medications used in respiratory treatment. For example, a high frequency chest wall compression pattern in combination with a controlled flow rate of inhalation and exhalation may produce improved aerosol deposition.
Consequently, there is a need for a single, multi-function pneumatic chest compression system that can provide the variable types and patterns of chest compressions described above, as well as perform, or operate with other devices that perform, the various related functions (e.g., detecting inhalation and exhalation) described above. Such a system would be particularly useful in a clinical environment for both diagnostic and treatment applications, but could also be used in a long-term treatment environment.
In addition to the multiple functions described above, a chest compression device should be safe to operate. Any type of unexpected or uncontrolled increase in chest compression could injure a patient or deter use of the device. This is particularly true concerning patients with a respiratory ailment where the ability to recover from such increased chest compressions may be limited or more difficult. Consequently, a chest compression system should limit, if not eliminate, the possibility of unintended or uncontrolled increases in chest compression.